04Silverado5.3

With the power window switch at rest (no input) both pins at the motor will be grounded. The way the motor is controlled the drivers door module (DDM) provides a ground to the motor on both pins until the switch is moved. When the switch is selected to move the window up, 12 volts will be supplied to dark blue wire and the motor will be grounded on the brown wire. When the switch is selected to lower the window the polarity is reversed and 12 volts is supplied on the brown wire and ground is on the dark blue wire.

The way I always tested for power and ground was to disconnect the connector at the motor and connect at test light across the 2 terminals and then operate the power window switch. The test light should light in both directions (up and down). If the test light illuminates in both directions the motor is bad. Motor failures are less common than the regulator cables breaking, but the motors do fail.